Using AI to restore old films from early times?

Well, I don’t think it’s possible to restore audio to something that lost the audio without it sounding weird or creepy, as AI tends to be. If, say you wanted to restore the audio for the uncut Friday the 13th part 2 gore footage, we would need behind the scenes footage of them shooting those scenes, extract the audio, do some restoration work on that, and then stitch that over the heavily-damaged VHS footage that we currently have.

That’s just a guess though.

I'll do that as soon as the guru scene is found for Willy Wonka and the Chocolate Factory

Basically, on the original reel for Wonka, a scene was featured where a man climbs a hill to find a guru and ask him the meaning of life, but the guru asks for a Wonka bar, and when he realizes that it doesn't have a golden ticket, he looks, sadly, and says "Life? Life is a disappointment..." The scene was cut from later releases, including theater, because it wasn't funny to the big guys.

The "static-y" imagery is called grain, and grain is what an image in film is literally made out of. Removing it is something that's to be done with extreme caution and usually doesn't end too well, and when it does look good it's because some of it is still left in. Also, I'm not entirely sure why you want to "restore" a song from a movie that's already had its soundtrack officially released multiple times and has been released on bluray many times scanned directly from the negatives. What is there to restore, exactly?

AI still has a long way to go in restoring anything. Colorizing black and white movies (many of which were filmed with them being black and white in mind) is already controversial, and every attempt at using AI to colorize them looks like a disgusting muddy mess. AI upscaling also tends to smooth things out and introduce weird artifacts, it's just not worth it if it doesn't look any better than the original.